(1) Field of the Invention
The invention relates to a carrier structure for mounting light-emitting diode (LED) chips, more particularly to the carrier structure that can provide superior shuttering protection for the LED chips mounted thereon.
(2) Description of the Prior Art
Various merits of a typical LED product can be found; such as a long service life, a reduced size, high vibration resistance, low heat generation, low energy consumption and so on. Hence, the LED products are widely applied to various indicators and light sources for household and/or workplace usage. Recently, the trend in the LED technology is moving toward color and high-illumination products, and the application of the LEDs has been extended to large-scaled outdoor displaying, traffic signaling and the like. It can be foreseen that the LED with its features in energy saving and green powering will definitely become the mainstream in future illumination industry.
However, the LED is vulnerable in usage. For example, the LED cannot sustain abnormal electric currents to flow by, and cannot afford to carry a higher electric voltage, either. Generally, while in facing those incidents, the LED would be broken so as to lead to a short circuit or an open circuit.
In the art, a protection circuit is usually used to protect the LED by paralleling to the LED chip. While in meeting an unexpected (high) surge voltage, the extra voltage will be shared by the protection circuit, and the LED chip in the parallel circuit can thus be saved.
Nevertheless, it would degrade the illumination efficiency of the LED chip if both the LED chip and the protection circuit are constructed close to each other at the same bonding surface. Referring to FIG. 1, a typical LED packaging is shown. The package to mount the LED chip 20 includes a housing 40 and a lead frame 30. The LED chip 20 wired to the lead frame 30 is laid on the housing 40 in a concave room thereof. The protection circuit 50 also laid in the concave room and wired to the lead frame is arranged neighborly to the LED chip 20. It is noted that the LED chip 20 and the protection circuit 50 are posed in an electric parallel relationship in the package of FIG. 1.
By providing the arrangement of the LED chip 20 and the protection circuit 50 in the package as shown in FIG. 1, a shuttering effect would be formed to degrade the illumination of the LED chip 20. Moreover, the illumination pattern of the LED chip 20 might be altered to some extent. An alternative to the design of FIG. 1 is shown in FIG. 2, in which the protection circuit 50 is located under the LED chip 20 by being buried into the housing 40′. However, though the shuttering problem of the design in FIG. 1 might be resolved by the design of FIG. 2, yet the cost for this change would be considerable and yield of the package of FIG. 2 would be lower by compared to that of FIG. 1.